Dravet syndrome (DS), a catastrophic childhood epilepsy, is associated with severe intellectual disability, impaired social development, persistent drug-resistant seizures and a high risk of sudden unexpected death in epilepsy. We recently began to explore the possibility that single-gene mutations in zebrafish can be used to advance our understanding of the pathophysiology and treatment of DS. Zebrafish mutants featuring a loss-of- function sodium channel (SCN1A) mutation (e.g., a gene family commonly identified in children with DS) were identified and characterized by our laboratory as epileptic zebrafish with phenotypes similar to the human condition. Using automated behavioral tracking and in vivo electrophysiology assays we screened more than 1300 compounds using these fish. With the data generated, we now propose to extend this research program to include novel DS zebrafish mutants, additional high-throughput screening, and mechanistic analysis of a small molecule lead compound that emerged from the first screening effort. Three specific aims are proposed: (i) to generate and characterize zebrafish DS mutants, (ii) to perform high-throughput drug screening using zebrafish DS mutants, and (iii) to examine the mechanism of action for clemizole in DS mutants. Techniques will include automated locomotion tracking, in vivo zebrafish electrophysiology recording, pharmacology, CRISPR/Cas9 genome editing and calcium imaging using genetically encoded calcium indicators. Our results promise to advance our long-term goal to better understand the pathophysiology of genetic epilepsies, and identify promising new treatment options for these intractable conditions.